We are using a superior model for stroke to characterize this process and evaluate therapies. Waking monkeys are studied to avoid the confusing effects of anesthesia. The middle cerebral artery (MCA) is occluded with a ligature for varying periods of time to cause focal brain ischemia. We then study neurologic performance and cerebral blood flow. After two weeks of study, animals are sacrificed for pathologic examination. Results indicate that response to MCA occlusion is variable but predictable from blood flow data. We next aim to produce standardized strokes by partial MCA occlusion, guided by blood flow responses. This will lead to meaningful studies of therapy for standardized experimental stroke. BIBLIOGRAPHIC REFERENCES: Crowell, RM and DeGirolami U. Transient focal cerebral ischemia in waking monkeys. In Blood Flow and Metabolism in the Brain. Harper et al. eds. Aviemore, Scotland, June, 1975. Morawetz RB, DeGirolami U, Ojemann RG, Marcoux FW, and Crowell RM. Cerebral blood flow determined by hydrogen clearance during focal cerebral ischemia in waking monkeys. Stroke 8: 138, 1977.